Using GIS as a means of modelling work rates and as a decision support tool in alien plant control management : the case study of the eMpofana river, KwaZulu-Natal Midlands.

Abstract:

The problems posed by alien invasive plants to our environment and the need for
clearing and control has been highlighted by the Working for Water (WFW)
programme. Alien plant control requires careful planning, including budgeting. To
date, costing and budgeting in alien plant control has largely been a combination of
experience on the part of weed 'experts', coupled with much guess work. Weed
controllers have through experience calculated the amount of time (or the work rate),
recorded as labour days, required for different control actions of different weed
habits. These work rates are for weed clearance under ideal conditions and do not
take into account the effect of factors such as gradient, access and distance to the
weed infestation.
Factors affecting the work rate has been researched and modelled by researchers
in both alien plant control and the timber industry. While the existing work rate
model is useful in its present theoretical state, the model may be improved upon to
make it more practical and applicable to the varying conditions of different areas.
This research built on existing theoretical research on alien control work rates, and
concentrated on two main areas: the adaption and incorporation of the existing
research on work rates into a Geographical Information System (GIS), and the
creation and demonstration of a Spatial Decision Support System (SDSS) for the
management of alien plant control. The eMpofana river in the KwaZulu-Natal
midlands was selected as the study area, as there was an existing alien plant control
programme.
Initially all factors, such as slope, access to weed infestations, terrain and
penetrability of infestations, affecting the work rate in the research area were
identified. An existing work rate model was then modified to account for the
conditions of the research area. Regression analysis was used to derive the
relationship between the various factors affecting work rate, creating a work rate
model applicable to the study area. Using the results of the regression analysis together with work rate figures adapted
from an existing alien plant control programme, a SDSS for alien plant control along
the eMpofana River was created. The use of the work rate model and the SDSS in
the development of weed control programmes was demonstrated by examining four
different management approaches, each having a different management objective .
The SDSS provides a spatial component to weed control planning and costing that
has thus far not existed.
What this research has achieved is the advancement of an alien control work rate
model from a theoretical to a more realistic costing process. While some factors
affecting work rate may not have been accounted for, the model does address the
present inaccuracies in labour costing, and ultimately alien plant control costing. The
research has highlighted the disadvantages of GIS in terms of affordability and
expertise.
The model has wider uses than the eMpofana River, and is the ground work for the
further development of a user friendly model applicable throughout South Africa.
More effective project budgeting will decrease the likelihood of project failure and this
will directly benefit long-term weed control efforts.